Canon has built up a big inventory of cameras prior to the announcement, according to a Chuck Westfall Interview, and they will likely be sending them by sea all over the world at about the same time. There might be a week or two between deliveries in different countries, but they should all be pretty close. China seems to start selling first, I guess its a shorter boat trip for them to get to China.
I think that they are supposed to hold them and start on the same day, but that never happens.
